Voltage regulator



May 8, 1956 J SNYDER 2,745,022

VOLTAGE REGULATOR Filed Jan. 5, 1954 SECOND (men) CURRENT VOLTAGE SUPPLY-0 FIRST (LOW) CONTROL 22 VOLTAGE SUPPLY LOAD DETECTOR O- '2 FIG I \26INVENTOR.

JAMES SNYDER ATTORNEY United States Patent VOLTAGE REGULATQR JamesSnyder, Asbury Park, N. J assignor to the United States of America asrepresented by the Secretary of the Army Application January 5, 1954,Serial No. 402,417

Claims. (Cl. 307-43) (Granted under Title 35, U. 5. Code (1952), see.266) The invention described herein may be manufactured and used by orfor the Government for governmental purposes, without the payment of anyroyalty thereon.

This invention relates to voltage regulators and more particularly tomeans for controlling a low voltage supply.

The voltage regulation systems well known in the art usually rely on avariable resistance in the form of a vacuum tube between the source ofvoltage and the load to supply a substantially constant current orvoltage to a given load. Other systems include applying the variableresistance tube in parallel with the load to draw more or less currentthrough a common series resistor from the power supply to compensate forvariations in the load or power supply. These systems are generallyapplicable to high voltage power supplies since they require asubstantial voltage in excess of the voltage on the load as part of thecontrol circuit and to be within the useful range of the control of thevacuum tube.

The problems of control of a low voltage are much more difiicult sincethe current is comparatively greater for the voltage involved and thecurrent may be excessive for a vacuum tube while the voltage may not begreat enough to operate the vacuum tube. The voltage regulating circuitof this invention uses a series resistor connecting the load to the lowvoltage power supply. This series resistor is effectively a volta esource since it is included in a second variable electronic circuitwhich need only supply the necessary current or voltage to compensatefor the changes in the load. A variation of this circuit includes abridge rectifier in place of or in conjunction with the voltage droppingresistor in series with the load. An alternating current controlled bythe variations in voltage across the load is applied through the bridgeto compensate for the changes in the voltage acres the load.

It is, therefore, an object of this invention to provide a voltageregulator.

It is a further object of this invention to provide a means in serieswith a load for compensating for the variations in the supply of voltageor current to the load.

It is a further object of this invention to provide a voltage regulatorcircuit applicable to low voltages.

It is a further object of this invention to provide a voltage regulatingcircuit that does not draw power back from the voltage supply beingregulated.

Other and further objects of this invention will become apparent fromthe following specification and the drawings of which:

Figure 1 shows the basic concept of this invention in block diagrammaticform; and

Figure 2 shows a typical circuit for accomplishing the low voltageregulation.

Referring now more particularly to Figure l, a low voltage supply acrossterminals 1d and 12 provides energy through resistance 14 for a load 16.A second voltage supply which may be of substantially higher voltagethan the first is applied across terminals 20 and 22 through the.dropping resistor 14 and a current control 24. The load 2,745,022Patented May 8, 1956 voltage actuates the detector 26 which regulatesthe current control 24.

In operation a variation in the voltage across the load 16, which may bethe result of a variation in the internal impedance of the load or avariation in the voltage of the first voltage supply, applies a signalto the detector 26 which may be the grid of a vacuum tube or any ofseveral means, well known in the art, sensitive to variations in voltageor current. For critical purposes the variations detected may beamplified in voltage or in power to provide a stronger signal for a moreprecise control of the current from the second voltage supply. Thecurrent control 24 causes more or less current to flow through theresistance 14 which indirectly adds or subtracts to the voltage acrossthe load 16 until its correct operating voltage is restored to rebalancethe detector.

In Figure 2 the resistance 14 may be replaced by rectifier bridge 30,although a variable resistance 32 may also be provided, in series withthe load 216 across the low voltage supply 210 and 212. In this circuitthe detection and current control is realized by a sampling circuitwhich transfers the variation in voltage across the load to aproportional modulation of a relatively higher frequency alternatingcurrent. This is amplified and applied back to the bridge 30 to providea voltage to compensate for any variation in the load.

In operation the voltage level across the load 216 is applied to thegrid of tube 226 whose cathode circuit is keyed by the multivibrator 40to gate or sample the signal. The output of tube 226 at 42 is anamplitude modulated envelope of the frequency of multivibrator 40. Thisis applied to tube 44 which may be biased by network 46 to increase theratio of modulated to unmodulated signal. The output of tube 44 at 43 ispassed through a second limiting circuit 50 including diode 52 to obtaina still greater percentage of the modulation of the multivibratorfrequency across the tuned circuit 54. This is adjusted to thefrequencyof the multivibrator and acts as a filter to provide a better waveformfor the modulated frequency by reducing the peaks and harmonics of theoriginal square waveform. The amplified and filtered modulation envelopeis passed through tube 56 which is transformer coupled to push-pullstage 58 for power amplification. The output of the push-pull stage 58is transformed in 60 to the level voltage to be applied across terminals36 and 38 of bridge 30 which rectifies and applies D. C. voltage inseries with the low voltage supply.

In operation the variations in voltage across the load 216 aretransformed into modulated high frequency energy to be amplified andfiltered and applied back across the rectifier which adds or subtractsthe necessary voltage to restore the voltage across the load tosubstantially its correct value.

While this circuit is useful primarily in low voltage circuits Whererelatively few forms of voltage regulation of a satisfactory or adequatenature are available, it would be obvious to anyone skilled in the artthat this form of voltage regulation could also be advantageouslyapplied to high voltage systems.

The limiting factor in the voltage control is the stray or undesiredfeedback in the amplifier, particularly between the high and low levelsections of an amplifier as shown in Figure 2; however, in practice withgood shielding techniques a regulation of better than 1% can beachieved. The circuit of Figure 2 utilizing sampling techniques canprovide regulation not only of alternating current variations but alsoof substantially direct current variations while still using relativelysimple alternating current techniques of amplification. Having thusdescribed my invention what is claimed is:

1. In a control for low voltages, below the normal operating potentialsof vacuum tubes, a first low voltage supply, a voltage-droppingresistance, a load connected in series with said voltage-droppingresistance across said first voltage supply, a second low voltagesupply, a current regulating device connected in series with saidvoltagedropping resistance across said second voltage supply, means fordetecting the voltage variations across said load, said detecting meansconnected to said current regulatng device to vary the current of saidsecond voltage supply through said voltage-dropping resistance tocompensate for the variations in voltage across said load.

2. 'In a voltage regulator, a low voltage supply, a rectifier bridge, aload connected in series with one pair of arms of said rectifier bridgeacross said voltage supply, an alternating current source, means formodulating said alternating current source in accordance with thevariations involtage across said load, means for coupling the modulatedalternating current output to a second pair of arms of said bridge.

3. A low voltage supply, a rectifier bridge having a first and secondpair of arms, a load connected in series with the first pair of arms ofsaid rectifier bridge across said voltage supply, means for detectingvariations in voltage across said load, an oscillator, said oscillatormodulated by said detecting means, means for amplifying the modulatedoscillations, means for transforming said modulated oscillations to alow impedance circuit, said low impedance circuit connected across theother two arms of said rectifier bridge to compensate for variations involtage across said load.

4. In a voltage supply circuit as in claim 3, said oscillator being inthe form of a multivibrator.

5. A low voltage supply, a load, a variable resistance, a rectifierbridge having a first two terminals connected in series with saidvariable resistance and said load across said voltage supply, a vacuumtube actuated by the voltage across said load, a multivibrator circuitconnected to gate said vacuum tube, means for amplifying the output ofsaid vacuum tube, means for increasing the proportion of modulation ofthe output of said vacuum tube, means for transforming the output ofsaid vacuum tube to a lower impedance output, means for connecting thelower impedance output across a second two terminals and said rectifierbridge to compensate for the variations in voltage across said load.

References Cited in the file of this patent UNITED STATES PATENTS1,893,767 Fitzgerald et al. Jan. 10, 1933 2,035,263 Cushman et al. Mar.24, 1936 2,098,370 Bartels Nov. 9, 1937

